A Multi-omic Atlas of Human Choroid Plexus in Alzheimer's Disease.

The choroid plexus (CP) regulates barrier integrity, cerebrospinal-fluid (CSF) dynamics, and immune surveillance, yet its role in Alzheimer's disease (AD) remains poorly defined. We performed snRNA-seq on CP samples from 69 ROSMAP participants spanning normal cognition, mild cognitive impairment, and AD dementia, and integrated these data with spatial transcriptomics, snATAC-seq, and proteomics from CP tissue and CSF. We identified 17 CP cell states and uncovered widespread disease-associated transitions that converged into three major phenotypic axes. Along the inflammatory axis, epithelial cells and border-associated macrophages (BAMs) showed progressive immune activation, with BAMs shifting from inflammatory to stress-dominant states. In the barrier axis, epithelial cells, fibroblasts, and endothelial cells exhibited reduced junction-related gene expression and broad alterations in transport pathways. Epithelial cells also showed late-stage cilia loss and CSF-regulatory pathway impairment, indicating a breakdown in epithelial polarity and CSF sensing, consistent with abnormal CSF proteomic signatures. Along the remodeling axis, fibroblasts showed ECM alterations, while epithelial and stromal cells demonstrated aberrant cell-matrix adhesion pathways. Spatial neighborhood analysis revealed a multicellular signaling hub, with epithelial-rich niches showing the strongest dysregulation in AD. Together, these findings define a unified model of CP dysfunction in AD and position the CP as an active, multicellular contributor to AD pathophysiology.